The invention relates to daylight developing machines, wherein film to be developed is transported in succession through a film strip attachment station, an infeed accumulator, processing fluid stages, drying stages and to a discharge station.
In daylight developing machines of the general type referred to above, it is now common to develop not only motion-picture film, but also still photograph film strips from different customers connected together to form a long strip. A significant problem is the provision of splices between the individual film strips. These must be capable of passing through the developing, fixing and bleaching solutions without coming apart and, above all, must be capable of withstanding the mechanical stresses to which they are subjected in passing through the developing machine.
It is known to feed into a continuously operating developing machine a supply of leader strip when the developing machine is to be shut down. In this way, when the developing machine is to be started up again, it is merely necessary to connect the leading end of the next film strip to be developed to the trailing end of the leader strip already in the machine. As soon as the unconnected trailing end of a film strip to be developed has been pulled out of the film strip supply cassette, one attaches to such trailing end the leading end of either another film strip from another supply cassette or else the leading end of a leader strip.
The strips, on their way from the strip attachment station to the processing fluid stages, pass through an infeed accumulator. The infeed accumulator accumulates a certain length of strip, for example 6 to 10 meters, for subsequent feedout. Specifically, when the trailing end of a strip which extends through the infeed accumulator and which has already entered the first processing fluid stage arrives at the strip attachment station, it is detained there during the attachment thereto of the leading end of another strip. In order that the feeding of strip into the processing stages not be interrupted during such detention, the accumulated strip in the infeed accumulator is allowed to feed out into the processing stages. When the attachment operation is completed, the trailing end of the strip previously detained is permitted to enter into and pass through the infeed accumulator. Meanwhile, the accumulator begins to accumulate a certain length of strip again, in preparation for the next such attachment operation.
One such infeed accumulator is comprised of two rows of guide rollers about which the strip within the accumulator is trained in a winding path. The upper row of guide rollers is fixedly mounted, whereas the lower row of guide rollers is mounted on a vertically displaceable rod. During normal operation, i.e., when the infeed accumulator has accumulated its full length of strip, the lower row of guide rollers is at the bottom of the accumulator. If the trailing end of the strip in the accumulator is detained at the strip attachment station, the length of strip within the accumulator decreases; as the accumulated strip is fed out into the first processing stage, the rod mounting the lower row of guide rollers rises toward the upper row of guide rollers thereby shortening the path of the accumulated strip.
When developing connected-together film strips, it has been discovered that most strip breakage results from mechanical stresses to which the strips are subjected and above all from those stresses which result from the entrainment of the strips about small-diameter guide rollers. If a splice is of low quality or if a film strip has in it to begin with a small tear, the film strip will break when passing around such a roller as early as during the travel of the film strip through the infeed accumulator. In fact, the probability that the film strip breakage will occur within the infeed accumulator amounts to about 85-95%. When the strip breaks in this way, it is necessary to open up the infeed accumulator and rethread it. Because a daylight developing machine is involved, the entire length of film strip within the accumulator will become exposed. Typically the length involved will be from about 6 to 10 meters. To avoid exposure of so much of the film strip, it is possible to permit the section of film strip downstream of the break to continue to be fed into the processing stages of the developing machine, with the section of film strip upstream of the break being wound back out of the infeed accumulator into the film strip supply cassette. The disadvantage of this approach is that when the broken section of film strip has passed completely through the developing machine, although it has been saved from exposure and indeed has been properly developed, it is necessary to thread a leader into the developing machine, so that the feeding of film strips to be developed into the machine can resume. The threading of a leader into an unthreaded developing machine is time-consuming and therefore costly.
With conventional developing machines, it is usual to arrange the individual processing stages of the machine one after the other in a continuous straight path leading from one to the other end of the machine. This arrangement of processing stages has the disadvantage that the operator of the machine must continually run back and forth between the infeed and discharge ends of the machine. Federal Republic of Germany Offenlegungsschrift 2,021,119 discloses a machine for developing motion-picture film in which the processing stages are arranged in the just-described manner, but with the film after passing through the drying stages being guided in rearward direction to the back side of the machine. However, the disadvantage in question is not avoided, because here again two operators must be employed, one to work at the infeed station at the front side of the machine, the other to work at the discharge station at the back side of the machine.
Besides attending to the infeed and discharge of film strips, the operator of a developing machine of the type in question must attend to other machine operations and to machine malfunctions which, likewise, may require him to run back and forth between different parts of the machine. In particular, the machine operator must make sure that feeding of film strips into the processing stages proceeds in a proper manner after film strip breakage.